Compound-reciprocating compressor



Aug. 20, 1929.

H. HOPFLER COMPOUND RECIPROCATING COMPRESSOR Filed Nov. 25 1927 2Sheets-Sheet 1 NVENTD {IL-MA,

Patented Aug. 20, 1929.

UNITED STATES PATENT OFFICE.

HANS HOPPLER. or WINTERTHUR, SWITZERLAND, ASSIGNOR TO THE FIRM or SULZERFBERES socIE'TE' ANONYME, or WINTERTHUR, SWITZERLAND.

COMPOUND-RECIPROCATING COMPRESSOR.

Application filed November 25, 1927, Serial No. 235,556, and in GermanyDecember 1, 1926.

The present invention relates to compound reciprocating compressors andhas for its object to provide an improved construction of suchapparatuswhich will permit a reduction in weight and in space occupiedas compared with compressors of equal output constructed in accordancewith previous proposals.

It has already been proposed to arrange the cylinders of suchcompressors in tandem either horizontally or vertically but with thisconstruction an excessive amount of space was occupied in the directionof length or of height of the apparatus. In addition several stuffingboxes were necessaryfrom which trouble might arise during operation. Inother known forms of compressor the cylinders were arranged side by sidebut here again a considerable amount of space was 2 occupied and severalsets of piston and connecting rods were necessary thus increasing theweight of the apparatus; also at least two stufling-boxes werenecessary. Attempts have been made to reduce the weight and spaceoccupied by providing a compressor of this type with a simpledifferential piston but it has been found that in such cases the workingpressures set up unequal tresses in the frame work and mechanism of thecompressor, and also caused a certain irregularity in running whichcould only be compensated by the provision of a large flywheel.

According to the present invention a compound reciprocating compressoris provided with a double-acting differential piston stepped on bothsides and adapted to compress the working fluid in stages and to deliver it to a final delivery chamber through an intermediate receiver.Preferably the inlet and outlet pipes and valves are so positioned onthe cylinder that changes of shape produced by stresses due to heatingcancel one another and, in addition, safety valves are provided whichconstitute by-pass valves, each of which is adapted to connect thesuction and delivery chambers of one stage, the number of valves beingequal to the number of stages employed. Conveniently the arrangement ofthese safety valves is such that the vessel into which the working fluidis normally discharged, for example, the condenser of a refrigeratingmachine, may be emptied when required by opening the safety valves andthus establishlng communication between the delivery and suctionchambers of the several stages.

The invention may be carried into practice in various ways but oneconstruction according thereto is diagrammatically illustrated by way ofexample in the accompanying drawings, in which Figure 1 shows alongitudinal section through a two-stage compressor,

Figure 2 is a section on the line 12-?) of Figure 1,

Figure 3 is a section on the line (ll-a, of Figure 1,

Figure 4 is a view in section on the line cc of Figure 3, and

Figure 5 is a diagram illustrating the arrangement of pipes hithertoused for the purpose of emptying the vessel into which the compressornormally delivers the working fluid.

In the construction illustrated in the drawings the compressor comprisesa central portion 1 and two cylinder heads 2 and 3 closed by covers 4and 5 respectively. Within the cylinder is adapted to recipro- Cate adouble-acting differential piston 6 operated by means ofa piston rod 7passing through a stuffing box 8. The inlet pipe 9 of the compressorwhich may be connected for example to the evaporator of a refrigeratingmachine opens out into the central portion 1 and conveys working fluidto the inlet valves 10 and 11 of the first stage I. The working fluid isdischarged from the cylinder of the first stage through outletvalves 12and 13 whence it passes through a pipe 14; connected to a receiver whichis not shown in the (drawing. This receiver is also connected to theinlet pipe 15 of the second stage II carried by the cylinder head 2.

The second stage of the compresser is constituted by the two outer endsor cylinder heads 2 and 3 and is provided with inlet valves 17 and 20and outlet valves 18 and 21, the valve 20 being connected to the inletpipe 15 by means of a conduit 19 while the outlet valve 21 is connectedto the discharge pipe 16 of the second stage through a conduit 26 shownin chain lines in Figure 1.

The manner of operation of the compressor is as follows. Assuming thepiston to be moving towards the left in Figure 1 then the workingsurface 22 of the first stage and the working surface 24 of the secondstage will deliver compressed fluid through the valves 12 and 18respectively, the fluid which passes through the valve 12 entering thereceiver while that which passes through the valve 18 is dischargedthrough the pipe 16 which may, for example, be connected to thecondenser of a refrigerating machine. At the same time working fluidwill be drawn in through the inlet 9 and inlet valve 11 of the firststage and also through the inlet 15, conduit 19 and inlet valve 20 ofthe second stage, the fluid which is drawn into the second stage comingfrom the receiver to which it has been delivered; under pressure by thefirst stage. On the return stroke of the piston towards the right inFigure 1 the fluid previously drawn into the first stage through thevalve 11 will be discharged through the valve 13 and'pipe 14 into thereceiver while that drawn into the second stage through the valve 20will be discharged through the valve 21, conduit 26 and pipe 16 into thecondenser. At the same time a further quantity of fluid will be drawn into the first stage through the pipe 9 and valve 10 this fluid comingfrom the evaporator. Simultaneously fluid will be drawn into the secondstage from the receiver through the pipe 15 and valve 17 so that at eachstroke of the piston a quantity of fluid is drawn into the cylinder ofeach stage while at the same time a quantity of fluid compressed duringthe previous stroke is discharged from the cylinder of each stage.

The suction chamber 27 and delivery chamber I of the first stage areconnected through a safetyvalve 28 constituting a bypassvalve shownFigure 2. Similarly the suction chamber 29 and the delivery chamber IIof the second stage are connected by asafety valve 30 (Figure 3) alsoconstituting a by-p'ass "alve. By turning these valves through 180degrees communication may be established between the conduit 31connected to thesuction chamber 29 and the conduit 32 connected to thedelivery chamber II so that the contents of the condenser mav returndirectly to the evaporator.

With this construction the arrangement of the pipes shown in chain linesin Figure 5 which were hitherto necessary for the emptying of thecondenser may be omitted. In Figure 5 the condenser is assumed to be atthe lefthand side of the diagram and hitherto when it was necessary toempty the condenser the valves 33 and 34 had to be closed so that thefluid was conveyed, as shown by the dotted arrows, through the pipe 35to the first stage of the compressor and then through the pipe 14.- intothe second stage whence it was discharged through the pipe 36 into theevaporator assumed to be disposed on the righthand side of the diagram.lVith the construction according to the pres ent invention the by-passvalves 28 and 30 permit the suction and delivery valves to beinterchanged when it is necessary to empty the condenser so that thepipes 35 and 36 can be dispensed with.

The inlet pipe 9 together with the inlet valves 10 and 11 through whichthe working fluid is drawn in at about "20 C. are positioned on thecylinder between the outlet valves 18 and 21 through which the fluidpasses at a temperature of about C. after being compressed in the firststage. This arrangement provides room for expansion of the cylinderheads 2 and 3 due to the increase in temperature. The outlet valves 12and 13 together with the outlet pipe 14 through which the compressedfluid passes from the first stage at a temperature of about60 G. aredisposed between the inlet valves 17 and 20 through which the workingfluid enters the second stage at a temperature of about 10 C. With thisarrangement of the valves the expansion of the central portion 1 due tothis higher temperature is balanced by the relative contraction of thecylinder heads so that changes of shape produced by stresses due toheating are avoided.

The cylinder heads may be attached to the central portion and thecylinder covers to the cylinder heads by any known method. Further, thecentral portion is designed to be symmetrical so that the suction sidemay be interchanged with the delivery side.

It will be appreciated that with a compressor according to the presentinvention only one stuffing box is necessary and the working pressure isused to the best advantage, while, in addition the compressor occupiesless space and weighs less than compressors of equal output hithertoproposed.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is:

1. In a compound reciprocating compressor, the combination of a cylindercomprising a central portion constituting a low pressure chamber, acylinder head connected to each end of said cylinder, said cylinderheads each having a portion therein constituting a high pressurechamber, and a double-acting differential piston stepped on both sidesmovably disposed in said chambers and adapted to compress the workingfluid in stages therein and to deliver said fluid to a final deliverychamber through an intermediate receiver.

2. A compound reciprocating compressor as set'forth in claim 5, saidcylinder having openings for inlet and outlet pipes so positioned thatchanges of shape produced by stresses in the cylinder structure due toheating cancel one another. 7

3. A compound reciprocating compressor as set forth in claim 5,including in the combination safety valves connecting the suction anddelivery chambers of said low and high pressure stages.

4. A compound reciprocating compressor as set forth in claim 5,including in the combination a safety valve on said cylinder connectingthe suction and delivery chambers of said low pressure stage and asafety valve on each of said cylinder heads connecting the suction anddeliver chambers of said high pressure stage, said safety valves beingadapted to be turned through 180 for emptying the vessel to bedischarged by the working fluid.

5. In a two-stage compound reciprocating compressor, the combination ofa cylinder having a central portion constituting a chamber of relativelylarge diameter, a cylinder head connected to each end of said cylinder,said cylinder heads each having a chamber therein of the same diameter,which diameter is less than that of said central chamber, and adouble-acting differential piston having a central portion of relativellarge diameter arranged in said central 0 amber and end portions ofequal but smaller diameter arranged in said cylinder head chambers, saidcylinder together with said cylinder heads having portions thereofconstituting an intermediate receiver adapted to receive the Workingfluid compressed in said chambers.

In testimony whereof I have aflixed my signature.

HANS HOPPLEB.

CERTIFICATE OF CORRECTION.

Patent No. 1,724,934. Granted August 20, 1929, to

HANS HOPPLER.

It is hereby Certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1,line 3, strike out the words "to provide", and line 28, for the word"tresses" read stresses";

page 2, lines 124 and 130, claims 2 and 3, and page 3, line 5, claim 4,for

"claim 5" read "claim 1"; and that the said Letters Patent should beread with these corrections therein that the same may conform to therecord of the case in the Patent Office.

Signed and sealed this 1st day of October, A. D. 1929.

M. J. Moore, (Seal) Acting Commissioner of Patents.

